13 Things That Don't Make Sense Read Online Free

shifted toward the
     blue end of the spectrum; the number of waves reaching you every second would get a boost from the motion of the rainbow’s
     approach. This is called a blueshift. If the rainbow was racing away from you, the number of incoming waves per second would
     be reduced and the frequency of radiation would shift downward toward the red end of the spectrum: a redshift.
    It is the same for light coming from distant nebulae. If a nebula were moving toward Slipher’s telescope, its light would
     be blueshifted. Nebulae that were speeding away from Earth would be redshifted. The magnitude of the frequency change gives
     the speed.
    By 1912 Slipher had completed four spectrographs. Three were red-shifted, and one—Andromeda—was blueshifted. In the next two
     years Slipher measured the motions of twelve more galaxies. All but one of these was redshifted. It was a stunning set of
     results, so stunning, in fact, that when he presented them at the August 1914 meeting of the American Astronomical Society,
     he received a standing ovation.
    Slipher is one of the unsung heroes of astronomy. According to his National Academy of Sciences biography, he “probably made
     more fundamental discoveries than any other twentieth century observational astronomer.” Yet, for all his contributions, he
     got little more than recognition on two maps: one of the moon, and one of Mars. Out there, beyond the sky, two craters bear
     his name.
    The reason for this scant recognition is that Slipher had a habit of not really communicating his discoveries. Sometimes he
     would write a terse paper disseminating his findings; at other times he would put them in letters to other astronomers. According
     to his biography, Slipher was a “reserved, reticent, cautious man who shunned the public eye and rarely even attended astronomical
     meetings.” The appearance in August 1914 was an anomaly, it seems. But it was one that set an English astronomer called Edwin
     Powell Hubble on the path to fame.
    The Cambridge University cosmologist Stephen Hawking makes a wry observation in his book The Universe in a Nutshell . Comparing the chronology of Slipher’s and Hubble’s careers, and noting how Hubble is credited with the discovery, in 1929,
     that the universe is expanding, Hawking makes a pointed reference to the first time Slipher publicly discussed his results.
     When the audience stood to applaud Slipher’s discoveries at that American Astronomical Society meeting of August 1914, Hawking
     notes, “Hubble heard the presentation.”
    By 1917, when Einstein was petitioning astronomers for their view of the universe, Slipher’s spectrographic observations had
     shown that, of twenty-five nebulae, twenty-one were hurtling away from Earth, with just four getting closer. They were all
     moving at startling speeds—on average, at more than 2 million kilometers per hour. It was a shock because most of the stars
     in the sky were doing no such thing; at the time, the Milky Way was thought to be the whole universe, and the stars were almost
     static relative to Earth. Slipher changed that, blowing our universe apart. The nebulae, he suggested, are “stellar systems
     seen at great distances.” Slipher had quietly discovered that space was dotted with myriad galaxies that were heading off
     into the distance.
    When these velocity measurements were published in the Proceedings of the American Philosophical Society , no one made much of them, and Slipher certainly wouldn’t be so vulgar as to seek attention for his work. Hubble, though,
     had obviously not forgotten about it. He asked Slipher for the data so as to include them in a book on relativity, and, in
     1922, Slipher sent him a table of nebular velocities. By 1929 Hubble had pulled Slipher’s observations together with those
     of a few other astronomers (and his own) and come to a remarkable conclusion.
    If you take the galaxies moving away from Earth, and plot their speeds against their